Error Incorrect Syntax Near '('. When Doing Update() From Code, VB

Hi all

My error is as follows:

 Incorrect syntax near '('.
Line 27:         acceptOrDeclineFriendship.UpdateParameters.Add("Response", answer)
Line 28:         acceptOrDeclineFriendship.UpdateParameters.Add("FriendID", friend_id)
Line 29:         acceptOrDeclineFriendship.Update()
Line 30:
Line 31:     End Sub

Bear with me... I have a page where i use a repeater control to list users who have requested to be friends with the currently online user. The 'getFriendRequests' query looks like this:

SelectCommand="SELECT * FROM Friends, UserDetails WHERE (Friends.UserID = UserDetails.UserID) AND (FriendID = @UserID) AND (ApprovedByFriend = 'False') ORDER BY Friends.Requested DESC">

This works. 

Within each repeater template, there are 2 buttons, 'Accept' or 'Decline', like this: <asp:Repeater ID="Repeater1" runat="server" DataSourceID="getFriendRequests">
<ItemTemplate>
(other stuff like avatar and username etc)
<asp:Button ID="accept" runat="server" Text="Accept" commandName="Accept" commandArgument='<%#Eval("UserID")%>' onCommand="Accept_Decline_Friends"/>
<asp:Button ID="decline" runat="server" Text="Decline" commandName="Decline" commandArgument='<%#Eval("UserID")%>' onCommand="Accept_Decline_Friends"/>
</ItemTemplate>
</asp:Repeater>

The code-behind (VB) which deals with this is as follows: Protected Sub Accept_Decline_Friends(ByVal sender As Object, ByVal e As CommandEventArgs)

'retrieve id of requestee and the answer accept/decline
Dim friend_id As String = e.CommandArgument.ToString
Dim answer As String = e.CommandName.ToString

'add the parameters
acceptOrDeclineFriendship.UpdateParameters.Add("Response", answer)
acceptOrDeclineFriendship.UpdateParameters.Add("FriendID", friend_id)
acceptOrDeclineFriendship.Update()

End Sub

Since the buttons are being created dynamically, this is how i track 1. the response from the currently logged in user 'Accept/Decline' and 2. who they are responding to (by their uniqueid)

This relates to a sqlDataSource on my .aspx page like this: <!---- update query when user has accepted the friendship ---->
<asp:SqlDataSource ID="acceptOrDeclineFriendship" runat="server" ConnectionString="<%$ xxx %>"
UpdateCommand="UPDATE Friends SET (ApprovedByFriend = @Response) WHERE (FriendID = @UserID) AND (UserID = @FriendID)">
<UpdateParameters>
<asp:ControlParameter Name="UserID" ControlID="userIdValue" />
</UpdateParameters>
</asp:SqlDataSource>

 Which is meant to update my 'Friends' table to show that 'ApprovedByFriend' (the logged in user) is either 'Accept' or 'Decline', and record who's request was responded to.

I hope this is clear, just trying to suppy all of the information! The error appears to be saying that I have an issue with my code-behind, where i am telling the sqlDataSource above to UPDATE. What I can say is that for each button in the repeater, the 2 variables 'friend_id' and 'answer' are picking up the correct values.

Can anyone see any obvious problems here? Any help is very much appreciated as i am well and truley stuck!